From what I've read and gatheres in reading many reviews on eHam for the Heil "Clear Speech" unit and others mfr's:
a) Doesn't function well in a vehicle.
b) Must be grounded for proper operation.
c) Apparently, no company that offers this product has a trouble-free record with them including Heil.
d) Inconsistent - people either like them or hate them - no consensus despite the fact that eHam had 4 pages of user reviews on this item with an average of 4.0 because there were enough dissatisfied owners.
e) RF getting into and affecting speaker/dsp functions - this seems to be a re-occurring theme.
f) A bit too big - uses up a lot of space.
g) Quit working altogether.
What gets me about these units, is that the same electronics is currently being used for hands-free cell phones - and costing dimes on the dollar compared to what the Ham units sell for. I didn't think you would be surprised with that concept.
The breakdown rate is strangely high. Regardless of who makes them - this isn't just a Heil problem. The cell phones units don't seem to be suffering from the same maladies - either. Maybe now is not the time to buy one of these. Not until the price gets reduced, they fix the bugs that make them break, and have a more powerful amp to drive a better quality speaker than they have been putting in these things.